1 /*
2 * xor.c : Multiple Devices driver for Linux
3 *
4 * Copyright (C) 1996, 1997, 1998, 1999, 2000,
5 * Ingo Molnar, Matti Aarnio, Jakub Jelinek, Richard Henderson.
6 *
7 * Dispatch optimized RAID-5 checksumming functions.
8 *
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation; either version 2, or (at your option)
12 * any later version.
13 *
14 * You should have received a copy of the GNU General Public License
15 * (for example /usr/src/linux/COPYING); if not, write to the Free
16 * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
17 */
18
19 #define BH_TRACE 0
20 #include <linux/module.h>
21 #include <linux/gfp.h>
22 #include <linux/raid/xor.h>
23 #include <linux/jiffies.h>
24 #include <asm/xor.h>
25
26 /* The xor routines to use. */
27 static struct xor_block_template *active_template;
28
29 void
xor_blocks(unsigned int src_count,unsigned int bytes,void * dest,void ** srcs)30 xor_blocks(unsigned int src_count, unsigned int bytes, void *dest, void **srcs)
31 {
32 unsigned long *p1, *p2, *p3, *p4;
33
34 p1 = (unsigned long *) srcs[0];
35 if (src_count == 1) {
36 active_template->do_2(bytes, dest, p1);
37 return;
38 }
39
40 p2 = (unsigned long *) srcs[1];
41 if (src_count == 2) {
42 active_template->do_3(bytes, dest, p1, p2);
43 return;
44 }
45
46 p3 = (unsigned long *) srcs[2];
47 if (src_count == 3) {
48 active_template->do_4(bytes, dest, p1, p2, p3);
49 return;
50 }
51
52 p4 = (unsigned long *) srcs[3];
53 active_template->do_5(bytes, dest, p1, p2, p3, p4);
54 }
55 EXPORT_SYMBOL(xor_blocks);
56
57 /* Set of all registered templates. */
58 static struct xor_block_template *template_list;
59
60 #define BENCH_SIZE (PAGE_SIZE)
61
62 static void
do_xor_speed(struct xor_block_template * tmpl,void * b1,void * b2)63 do_xor_speed(struct xor_block_template *tmpl, void *b1, void *b2)
64 {
65 int speed;
66 unsigned long now;
67 int i, count, max;
68
69 tmpl->next = template_list;
70 template_list = tmpl;
71
72 /*
73 * Count the number of XORs done during a whole jiffy, and use
74 * this to calculate the speed of checksumming. We use a 2-page
75 * allocation to have guaranteed color L1-cache layout.
76 */
77 max = 0;
78 for (i = 0; i < 5; i++) {
79 now = jiffies;
80 count = 0;
81 while (jiffies == now) {
82 mb(); /* prevent loop optimzation */
83 tmpl->do_2(BENCH_SIZE, b1, b2);
84 mb();
85 count++;
86 mb();
87 }
88 if (count > max)
89 max = count;
90 }
91
92 speed = max * (HZ * BENCH_SIZE / 1024);
93 tmpl->speed = speed;
94
95 printk(KERN_INFO " %-10s: %5d.%03d MB/sec\n", tmpl->name,
96 speed / 1000, speed % 1000);
97 }
98
99 static int __init
calibrate_xor_blocks(void)100 calibrate_xor_blocks(void)
101 {
102 void *b1, *b2;
103 struct xor_block_template *f, *fastest;
104
105 /*
106 * Note: Since the memory is not actually used for _anything_ but to
107 * test the XOR speed, we don't really want kmemcheck to warn about
108 * reading uninitialized bytes here.
109 */
110 b1 = (void *) __get_free_pages(GFP_KERNEL | __GFP_NOTRACK, 2);
111 if (!b1) {
112 printk(KERN_WARNING "xor: Yikes! No memory available.\n");
113 return -ENOMEM;
114 }
115 b2 = b1 + 2*PAGE_SIZE + BENCH_SIZE;
116
117 /*
118 * If this arch/cpu has a short-circuited selection, don't loop through
119 * all the possible functions, just test the best one
120 */
121
122 fastest = NULL;
123
124 #ifdef XOR_SELECT_TEMPLATE
125 fastest = XOR_SELECT_TEMPLATE(fastest);
126 #endif
127
128 #define xor_speed(templ) do_xor_speed((templ), b1, b2)
129
130 if (fastest) {
131 printk(KERN_INFO "xor: automatically using best "
132 "checksumming function: %s\n",
133 fastest->name);
134 xor_speed(fastest);
135 } else {
136 printk(KERN_INFO "xor: measuring software checksum speed\n");
137 XOR_TRY_TEMPLATES;
138 fastest = template_list;
139 for (f = fastest; f; f = f->next)
140 if (f->speed > fastest->speed)
141 fastest = f;
142 }
143
144 printk(KERN_INFO "xor: using function: %s (%d.%03d MB/sec)\n",
145 fastest->name, fastest->speed / 1000, fastest->speed % 1000);
146
147 #undef xor_speed
148
149 free_pages((unsigned long)b1, 2);
150
151 active_template = fastest;
152 return 0;
153 }
154
xor_exit(void)155 static __exit void xor_exit(void) { }
156
157 MODULE_LICENSE("GPL");
158
159 /* when built-in xor.o must initialize before drivers/md/md.o */
160 core_initcall(calibrate_xor_blocks);
161 module_exit(xor_exit);
162